President Obama’s spokesman confirmed Thursday that White House officials asked the Pentagon in May about Defense Secretary Ashton Carter’s use of a personal email account for some official business, but didn’t indicate any followup to learn whether he he stopped the practice.

But he had no explanation for why Mr. Carter apparently continued to use the personal account until a few months ago.

After former Secretary of State Hillary Clinton’s scandalous use of a private email server to conduct government business, Mr. Earnest said there is “no ambiguity” that government employees shouldn’t engage in the practice. But he couldn’t say for certain whether any other Cabinet members might be doing so.

“If there are, this surely is another reminder of why that would be a poor choice,” Mr. Earnest said.